The present invention relates to an optical disk and a method of playing back from an optical disk.
FIG. 29 is a block diagram showing a conventional optical disk recording/playback device shown in Japanese Patent Kokai Publication 114369/1992. An A/D converter 1 converts a video signal, an audio signal or the like into digital information. An information compressing means 2 serves to compress the output of the A/D converter 1. A frame sector converting means 3 converts the compressed information into sector information equal in length to a multiple of the frame period. An encoder 4 encodes the output of the frame sector converting means 3. A modulator 5 modulates the output of the encoder 4 into predefined modulated codes so as to reduce interference between codes on the recording medium. A laser driver 6 is for modulating the laser light in accordance with the modulated codes. A laser output switch 7 is driven by the laser driver 6 to vary the current supplied to the laser in an optical head 8, for emitting laser light.
An actuator 9 is for tracking the emitted light beam. A traverse or feed motor 10 is for moving the optical head 8 in the radial direction of a disk 12 which can record information by magneto-optical recording or phase-change recording.
A disk motor 11 is driven by a motor driver 19 to rotate the disk 12. The motor drivers 19 are controlled by first and second motor controllers 20. A playback amplifier 13 amplifies the playback signal from the optical head 8. A demodulator 14 demodulates the amplified playback signal to obtain data from the recorded, modulated signal. A decoder 15 decodes the demodulated signal, and a frame sector inverse conversion means 16 performs frame sector inverse conversion to restore original image data with the addresses and parities having been removed. An information expanding means 17 expands the compressed information, and a D/A converter 18 converts the expanded information into an analog video or audio signal.
FIG. 30 shows, in a simplified form, the data arrangement structure (layer structure) of the Moving Picture Coding Experts Group (MPEG) system which is a standard method of transferring and storing compressed digital moving picture information. In FIG. 30, reference 21 denotes a group of pictures (hereinafter referred to as xe2x80x9cGOPsxe2x80x9d) consisting of information of a plurality of frames, 22 denotes a GOP layer formed of several pictures (screens), 23 denotes slices into which each picture is divided, 24 denotes a slice layer formed of several macroblocks, 25 denotes a microblock layer, and 26 denotes a block layer formed of 8xc3x978 pixels.
The microblock layer 25 is a block consisting of 8xc3x978 pixels, which is the minimum unit of encoding in the MPEG system, and discrete cosine transform (hereinafter referred to as xe2x80x9cDCTxe2x80x9d) is effected taking each micro block as a unit. Four adjacent Y signal blocks and one Cb block and one Cr block which correspond, with regard to position, to the four Y signal blocks, i.e., six blocks in all form a macroblock 24. Several macroblocks 24 form a slice 23. The macroblock 24 is a minimum unit for motion compensated prediction, and the motion vector for the motion compensated prediction are determined taking each macroblock 24 as a unit.
FIG. 31 is a diagram showing the conventional encoding structure for the case where 17 pictures form one GOP. In FIG. 31, reference numeral 27 denotes an I-picture which is image information for which intra-frame DCT is effected, 29 denotes a P-picture which is image information for which forward motion-compensated DCT encoding is effected using the I-picture or another P-picture (P-picture other than the P-picture for which the forward motion-compensated DCT encoding is being effected) as a reference picture, 28 denotes a B-picture for which motion compensated DCT encoding is effected using the I-picture and/or P-pictures at preceding and succeeding positions, as reference pictures.
FIG. 32 is a diagram showing the conventional encoding structure for the case where 10 pictures form one GOP, and FIG. 33 is a diagram showing the conventional encoding structure for the case where 15 pictures form one GOP.
In the drawings, P-, B- and I-pictures are respectively represented as xe2x80x9cPxe2x80x9d or xe2x80x9cP-picture,xe2x80x9d xe2x80x9cBxe2x80x9d or xe2x80x9cB-picture,xe2x80x9d and xe2x80x9cIxe2x80x9d or xe2x80x9cI-picture.xe2x80x9d
The operation will next be described with reference to the drawings. With the advancement in the digital image information compression technology, it is now possible to realize an image filing system which is very convenient to use, by recording the compressed information on a disk, with which search is much easier than having a VTR with a magnetic tape. Since, such disk file system handles digital information, there is no deterioration due to dubbing, and because recording and reproduction is achieved optically and there is no direct contact with the recording medium, reliability is high.
Conventionally, an optical disk recorder shown in FIG. 29 is used for recording the digital compressed motion information of the MPEG system shown in FIG. 30. The image information digitized by the A/D converter 1 is converted at the information compression means 2 into information of a standard compression picture system such as an MPEG system. The compressed information is encoded and modulated so that the effects of the interference between the codes on the disk is reduced, and is then recorded on a disk 12. By making the amount of data for each GOP substantially identical, and by dividing information into sectors having a length equal to a multiple of a frame period, editing and the like, treating each GOP as a unit, is possible.
During playback, the image information reproduced from the optical disk 12 is amplified by the playback amplifier 13, and returned into a digital data by the demodulator 14 and the decoder, and the original image data with the addresses and parities having been removed can be restored at the frame sector inverse conversion means 16. Furthermore, an image signal is restored by effecting, MPEG decoding, for example, at the information expanding means 17, and is then converted into an analog signal by the D/A converter 18 so that display on a monitor or the like is possible.
If the MPEG system is used as the digital motion compression method as described above, the encoding structure comprising one or more compressed I-pictures 27 by means of intra-frame DCT, one or more P-pictures 29 which is formed of image information obtained by DCT encoding with motion compensation in the forward direction, and one or more B-pictures 28 obtained by DCT encoding with motion compensation using I- and/or P-pictures positioned in front and at the back along the time axis, as reference pictures, as shown in FIG. 31 to FIG. 33.
Because an I-picture is obtained by intra-frame DCT, is possible to effect reproduction of the image with an I-picture independently. A P-picture, on the other hand, is obtained by forward motion compensation and the reproduction of the image with a P-picture is not effected until after the reproduction of the I-picture. Because the B-picture is obtained by prediction from both sides, both the I- and/or P-pictures must first be reproduced before the B-picture. The amount of data is the smallest and the efficiency of encoding is the best with the B-picture, because it is predicted in both directions.
Because the B-picture is not reproduced independently, it requires an I- or P-pictures, so that if the number of the B-pictures is increased, the capacity of the buffer memories must be increased, and the delay time from the data input to the image playback is lengthened. In a storage media, represented by optical disks or the like, an encoding method with a high compression efficiency is desired for long-time recording and the delay in the image playback is not problematical. Accordingly, the encoding system showing in FIG. 31 to FIG. 33 is appropriate for simple playback.
Now let us consider how the conventional image search and fast playback are effected from a disk receding data with the encoding structure as described above. If the encoding structure is as shown in FIG. 33, and if playback is made by extracting I-pictures, fast playback is possible. In this case, when an I-picture is reproduced, then a track jump is conducted to access the next or preceding GOP, and the I-picture therein is reproduced. By repeating such an operation, a fast forward or reverse playback is realized. The feed speed for fast forward or reverse playback is limited to the 15-time speed in case of FIG. 33, and 10-times in the case of FIG. 32.
In the actual image search, if the speed is too high, it is difficult for the human eyes to recognize the image. For rough recognition, the fast search at a 10-time or more speed is appropriate, but for search with regard to the details after the rough search, fast playback or reverse playback at several-time speed is necessary It is therefore necessary that special playback can be conducted over a wide range, of from several tens to several times the normal playback speed, to permit effective image search. Where the compressed data of the MPEG system is used, and if it is attempted to reproduce P-pictures in the encoding structure of FIG. 31 to FIG. 33, the B-pictures positioned before the P-pictures are also read, and it is therefore difficult to realize four to eight time speed.
Since the conventional playback method reproduce the encoding structure on the disk as it is, special playback can be achieved only by I-pictures, and fast forward and reverse playback can be achieved only at a speed which corresponds to the number of frames contained in one GOP or a multiple thereof.
Also, with the recording format of the digital image shown in connection with the prior art examples, I-pictures, P-pictures and B-pictures are arranged in a sequence along the time axis, so that the special playback is limited to the following method.
Particularly, a fundamental method for special playback in the system for recording digital motion picture image in the prior art performs special playback using information recorded in the TOC area which is at the inner periphery of the disk. In this case, special playback is achieved by reading, in accordance with the head address of the scene change (the address of a location where a picture immediately after the scene change is recorded) or the head address of the image file recorded in the TOC area, the digital motion picture image of the I-picture stored at the address, and reproducing them in turn.
The conventional operation for reading from the optical disk in such a method is shown in the flowchart of FIG. 34. This flowchart shows the case in which special playback is effected on the basis of the address at the head of the scene in the motion picture image information recorded in the TOC area. First, a jump is made to the TOC area, and the scene head address is stored in the internal memory, and then jump is made to the address that has been stored, and the I-picture in the GOP to which jump has been made is reproduced, and displayed, and movement to the next address of jump destination is made. Such a sequence of operation is repeated.
With such a conventional method, however, a large amount of addresses which should be searched for (and to which a jump is destined) need to be stored, and the TOC information must be rewritten each time a recording is made.
Moreover, during special playback in the conventional system, it is necessary to skip B-picture data for reproducing P-pictures, but as the I-pictures, B-pictures and P-pictures are recorded on the disk in sequence, waiting time may have to be spent before reproducing a P-picture when a track jump is conducted.
Furthermore, in the conventional system the amount of data of the I-picture encoded by intra-frame DCT is larger than the amount of data of P- or B-pictures, so that super-fast playback, of several tens times the normal playback speed cannot be realized because the time for inputting data may be insufficient.
When starting a search in the conventional system for a desired GOP from an arbitrary position on the disk, the search operation must be repeated several times for finding the head of each GOP (at which time code or address of the image is recorded).
Furthermore, as the scene change position in the motion picture image information is not known, a scene-by-scene search for finding a scene cannot be achieved by using the conventional system.
In addition, because only part of the data in each GOP is read in the special playback, image playback may not be accomplished, or playback may be possible only with regard to part of the display screen in the conventional system.
An object of the invention is to increase the special playback speed.
Another object of the invention is to reduce rotation waiting time when a track jump is performed.
Another object of the invention is to enable continuous reproduction of I-pictures.
Another object of the invention is to reduce the capacity of memory for storing images during playback.
Another object of the invention is to facilitate locating the head position of each GOP.
Another object of the invention is to enable recording of information designating the manner of playback.
According to an aspect of the invention, there is provided an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using the data of the I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
wherein an address format is preformatted in front of the block of image information of said plurality of frames, and the data arrangement within each image information blocks is such that I- and P-pictures are collectively disposed.
Since the I- and P-picture data are collectively disposed, that is, the I- and P-picture data within each GOP are disposed in succession, they are read in succession during normal playback are stored in a buffer memory, and then decoded, and B-picture data are thereafter read and decoded sequentially to restore image data within the GOP. The capacity of the buffer memory can be reduced. During special replay, only I-picture data are read and decoded, while track jump can be effected at the position where the P- or B-picture data is recorded. During special replay, the time for reproducing P- and B-picture data can be omitted, so that the special playback speed can be increased.
It may be so arranged that a parity signal or header signal for recognition is recorded at the head of the I-picture data.
With the above configuration, the position detection of the I- and P-picture data and discrimination between the I- and P-picture data during fast playback can be made with ease, and continuous reproduction of I-picture data is achieved without reproducing the management data at the head of the GOP at the time of track jump.
It may be so arranged that the order of data arrangement of the I- and P-picture data within each of the image information blocks is different from one image information block to another image information block.
The configuration in which the order of data arrangement of the I- and P-picture data within each of the image information blocks is different from one image information block to another image information block can be implemented by exchanging the positions of the I- and P-picture data between adjacent image information blocks. With the above configuration, rotation waiting time at the time of track jump can be reduced.
It may be so arranged that the I- and P-picture data within each image information block are disposed adjacent to each other, and the order of data arrangement of the I-, P- and B-picture data is different from one image information block to another image information block.
The configuration in which the order of data arrangement of the I-, P- and B-picture data is different from one image information block to another image information block can be implemented by exchanging the positions of the I-, P- and B-picture data between adjacent image information blocks. With the above configuration, the rotation waiting time at the time of track jump can be further reduced.
It may be so arranged that the area within the optical disk is divided into a plurality of zones for respective radius ranges, the scanning linear velocities in different zones being substantially equal to each other, address data and a header signal being preformatted at the head of each of the image information blocks, and the number of data bits for each of the image information blocks being identical between the image information blocks, and the data recording bit length of the image information block within each sector being a multiple of the circumferential length of the track on the disk.
That data recording bit length of the image information block within each sector being a multiple of the circumferential length of the track on the disk means the recording capacity per image information block (GOP) is a multiple of the recording capacity per revolution. With the above configuration, the variation in the linear velocity can be restrained within a sufficient range, and the GOP head positions can be recognized with ease wherever position on the disk is being scanned.
It may so arranged that a mirror-surface part for track offset detection is provided for each of the image information blocks.
With the above configuration, it is possible to recognize the GOP head positions by reference to the mirror-surface parts, and by setting the length of the mirror-surface part to be different from other parts, the GOP head positions can be recognized from the sum signal at the optical head, without reproducing the data.
According to another aspect of the invention, there is provided an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using the data of the I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
wherein an address data preformatted in front of the respective image information blocks (or image files) are aligned on a straight line extending in the radial direction.
With the above configuration, wherever the light spot is tracing, the head position of each GOP can be recognized, and the track jump starting point can be defined accordingly
According to another aspect of the invention, there is provided an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using the data of the I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
wherein a jump destination address for special playback is recorded in the attribute data recording area at the head of each of the image information blocks.
With the above configuration, special playback can be conducted in any of different modes depending on the contents of the motion picture, and the manner of special playback can be designated during recording, and by repeating the track jump using the above information, special playback in which motion picture scene is completed or continuous reproduction of only the scene head portions can be achieved.
According to another aspect of the invention, there is provided an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using the data of the I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
wherein presence/absence of scene change detected from the temporal change in the luminance or chrominance information of the image is recorded in the attribute data recording area at the head of each of the image information blocks.
With the above configuration, it is possible to conduct image search by sequentially reproducing the still pictures immediately succeeding or immediately preceding the scene changes, and it is possible to conduct editing taking each scene (partitioned by the scene changes) as a unit, i.e., on a scene-by-scene basis.
According to another aspect of the invention, there is provided a method of playing back an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using said I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
wherein presence/absence of scene change detected from the temporal change in the luminance or chrominance information of the image is recorded in the attribute data recording area at the head of each of the image information blocks.
With the above configuration, it is possible to conduct image search by sequentially reproducing the still pictures immediately succeeding or immediately preceding the scene changes, and it is possible to conduct editing taking each scene (partitioned by the scene changes) as a unit, i.e., on a scene-by-scene basis.
According to another aspect of the invention, there is provided a method of playing back an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using said I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
said method comprising the steps of:
using an optical head having a coarse actuator for accessing to a desired position, and a fine actuator for jumping to a desired track at the inner or outer periphery of the optical disk;
playing back the I-picture data through search and identification by reference to the parity signal or the header signal within the image information block on the optical disk;
reproducing the I-picture data in the next image information block; and
repeating the above operations to perform fast playback or reverse playback.
With the above method, it is possible to reproduce I-pictures of the respective GOPs, by repeating track jump by referring to the parity or header signal at the head of each of the I-pictures.
According to another aspect of the invention, there is provided a method of playing back an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using said I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
said method comprising the steps of:
using an optical head having a coarse actuator for accessing to a desired position, and a fine actuator for jumping to a desired track at the inner or outer periphery of the optical disk;
playing back the I-picture data through search and identification by reference to the parity signal or the header signal within the image information block on the optical disk;
then playing back the P-picture data of a plurality of P-pictures successively;
conducting a track jump;
reproducing the I-picture data in the next image information block;
then playing back the P-picture data of a plurality of P-pictures successively; and
repeating the above operations to perform fast playback or reverse playback.
With the above method, the playback speed is improved.
According to another aspect of the invention, there is provided a method of playing back an optical disk wherein the rotational speed of the optical disk during fast playback or reverse playback of motion picture image is higher than the rotational speed of the optical disk during normal playback.
With the above method, the data transfer rate is improved.
According to another aspect of the invention, there is provided a method of playing back an optical disk wherein the rotational speed of the optical disk is raised in the region in which no data which need to be read during fast playback or reverse playback of a motion picture image is recorded, and is lowered to the linear velocity at which reproduction of data is possible, in the region in which I- and P-picture data is recorded.
With the above method, the overall playback speed is improved. It is also possible to achieve smooth fast special playback of motion picture image without using track jump.
According to another aspect of the invention, there is provided an optical disk recording digital image information in the form of a succession of image information blocks, each comprising I-picture data of an I-picture obtained by intra-frame DCT encoding, P-picture data of one or more P-pictures obtained by DCT encoding with forward motion compensation, and B-picture data of B-pictures obtained by DCT encoding with motion compensation using the data of the I- and/or P-pictures positioned in front and at the back thereof as reference pictures,
wherein said I-picture data is divided into fractional I-picture data for a plurality of regions into which a display screen is divided, and the fractional I-picture data are arranged in said image information block, and a header or parity signal is recorded in front of each fractional I-picture data.
It may additionally be so arranged that the fractional I-picture data in the adjacent image information blocks in the adjacent recording tracks may be different.
With the above configuration, through search for a header signal or parity signal recorded in front of the screen fractional I-picture data, the screen fractional I-picture data can be sequentially reproduced.
The header or parity signal is recorded at the head of the data obtained by dividing I-picture data for the respective regions in the screen, so that when conducting a special playback in which only I-pictures in the respective GOPs are reproduced and joined, it is not necessary to read all the I-picture data. Accordingly, the special playback speed multiplier is increased, and it is possible to obtain smooth continuous movement in the picture during the special playback.
According to another aspect of the invention, there is provided an optical disk in which DCT-encoded I-picture data is allocated into a plurality of sub-blocks according to the horizontal and vertical frequencies, from the DC components to the high-frequency components, sub-blocks of I-, P- and B-picture data in the adjacent image information blocks in the adjacent tracks are disposed with their order being altered, and a header or parity signal indicating which of the frequency components the content of each sub-block is for is recorded in front of each sub-block.
With the above configuration, the frequency-divided I-picture data of a desired low-frequency component can be arbitrarily accessed and sequentially reproduced by searching for the header or parity signal. As a result, is not necessary to read all the I-picture data if the resolution of the displayed picture may be sacrificed to a certain extent, and special playback speed multiplier is high and yet smoothly moving picture can be produced. Moreover, when zone CAV format disk is used, the rotation waiting time during special playback is reduced.
According to another aspect of the invention, there is provided an optical disk, in which DCT-encoded I-picture data is allocated into a plurality of sub-blocks according to the horizontal and vertical frequencies, from the DC components to the high-frequency components, the frequency-divided I-picture data within the adjacent image information blocks in the adjacent tracks are disposed differently, and a header or parity signal indicating which of the frequency components the content of each sub-block is for is recorded in front of each sub-block.
With the above configuration, it is possible to achieve high-speed fast playback or reverse playback of frequency-divided I-picture data by repeating track jump through search for the header signal or parity signal. That is, the frequency-divided I-picture data of a desired low-frequency component can be arbitrarily accessed and sequentially reproduced by searching for the header signal or parity signal. As a result, it is not necessary to read all the I-picture data if the resolution of the displayed picture may be sacrificed to a certain extent, and the special playback speed multiplier is high and yet smoothly moving picture can be displayed. Moreover, when zone CAV format disk is used, the rotation waiting time during special playback is reduced.
According to another aspect of the invention, there is provided an optical disk storing digital image information in the form of a succession of blocks, each comprising a plurality of frames comprising, in mixture, I-picture data forming image information obtained by intra-frame DCT encoding, P-picture data obtained by DCT encoding with forward motion compensation, and B-picture data obtained by DCT encoding with motion compensation using said I- and/or P-picture data positioned in front and at the back thereof as references,
wherein the digital motion picture image information is divided into lower-layer data having smaller numbers of pixels and lines, and upper-layer data which produce, in combination with the lower-layer data, an image with larger numbers of pixels and lines, and a header or parity signal for indicating the type of the data block is recorded in front of each data block.
It may additionally be so arranged that the lower-layer data and the upper-layer data are disposed, with their order being altered.
With the above arrangement, the digital motion picture image information can be sequentially reproduced through search for the header or parity signal and arbitrarily accessing I-picture data of desired, small numbers of pixels and lines. Moreover, it is not necessary to read all the I-picture data during special playback and yet image can be reproduced, and it is therefore possible to increase the special playback speed multiplier.
It may be so arranged that the order of data arrangement of I-, P- and B-picture data within an image information block is different between adjacent image information blocks.
With the above configuration, it is possible to achieve high-speed fast playback or reverse playback of screen-divided I-picture data by repeating track jump through search for the header or parity signal recorded in front of each data.
It may be so arranged that identification signal indicating whether the I-picture data is a screen-divided data, a frequency-divided data, or data divided by the numbers of pixels and lines is written at the head of each image information block.
With the above configuration, it is possible to identify whether the recorded digital motion picture image information is of an I-picture data, frequency-divided data, screen-region-divided data, or pixel/line-number divided data by finding an identification signal written at the head of each image information block and identifying the content thereof, and it is possible to sequentially reproduce the recorded digital motion picture image information.
It may be so arranged that the head positions of the digital image information blocks are aligned in the radial direction of the optical disk.
With the above configuration, it is possible to accurately determine the timings of the track jump, and to continuously read special playback data without rotation waiting time.
According to another aspect of the invention, there is provided a method of playing back from an optical disk comprising the steps of:
using an optical disk playback device comprising a tracking actuator for tracking a scanning spot on a predefined track, a tracking control circuit, and a track jump circuit for performing jumping scanning,
using an optical disk according to the descriptions above, and
repeating jumping operation on the basis of a header or parity signal recorded in front of each I-picture data to perform high-speed playback or reverse playback.
With the above method, it is thereby possible to perform high-speed playback or reverse playback of divided digital image information.
According to another aspect of the invention, there is provided a method of playing back from an optical disk, comprising the steps of:
using an optical disk playback device comprising a tracking actuator for tracking a scanning spot on a predefined track, a tracking control circuit, and a track jump circuit for performing jumping scanning,
using an optical disk according to the descriptions above, and
repeating jumping operation on the basis of an identification signal written at the head of each image information block to perform high-speed playback or reverse playback.
With the above method, it is possible to identify the type of the data of each image information block on the basis of an identification signal written at the head of each image information block, so that the digital image information can be reproduced.